Why are all of the calculators for calories different?

kiela64

I was keeping MFP at maintenance for a bit as I eased myself back in to tracking, but I wanted to check what lb/week rates I was hitting when I was eating less more consistently. I checked the first few calories-per-day-to-lose-weight calculators that I found on google. PrecisionNutiotion, Calculator.net, TDEE, and a few others. And they all gave me different answers despite using the same stats - 5’2, 200lbs, female, sedentary, etc.

I ended up just changing my goals on mfp a bunch of times to check what they all were, and mfp gave completely different numbers too! I was really surprised by this variance, when aren’t they all going for a 3500 cal = 1 lb of fat, super simple calculation? Especially if I set myself as sedentary for all of them there shouldn’t be any weirdness. But it was all different by about 100cal at least.

I’m absolutely going with MFP. But maybe someone knows why these are all different and what that means?

Edit: I had added examples but it didn’t post for some reason. Anyway, for 2lb/week, PN gives me over 1800cal, for MFP it’s a secret because it’s below 1200, and calculator. Net gives me 915. For 1lb/ week, PN gives me over 2000 which is higher than MFPs maintenance! Mfp gives me 1530, whereas calculator gives me 1427 and TDEE gives me 1433. It’s just all bizarrely different and I’m confused as to why that is.

malibu927

They do go by that, but they estimate in different ways. MFP uses the NEAT formula rather than TDEE. The difference between the two is how exercise is used...TDEE formulas already include exercise, whereas NEAT does not. This is why it’s expected that on MFP you would log and eat back your exercise calories. As for the differences in other calculators, that’s because they use different calculators to determine your TDEE. Remember that everything is just an estimate.

kiela64

malibu927 wrote: »

They do go by that, but they estimate in different ways. MFP uses the NEAT formula rather than TDEE. The difference between the two is how exercise is used...TDEE formulas already include exercise, whereas NEAT does not. This is why it’s expected that on MFP you would log and eat back your exercise calories. As for the differences in other calculators, that’s because they use different calculators to determine your TDEE. Remember that everything is just an estimate.

Yes, but they are all set to sedentary so they would all be then calculating without exercise. I double checked everything was at the lowest. I know they are estimates, and I would believe a variation of 50cal between them, but it gets so drastically different I found that very strange.

ladyreva78

There's countless different formulas to estimate Calorie requirements. Different calculators base themselves on different formulas and as a result give you a different estimate.

erickirb

kae612 wrote: »

malibu927 wrote: »

They do go by that, but they estimate in different ways. MFP uses the NEAT formula rather than TDEE. The difference between the two is how exercise is used...TDEE formulas already include exercise, whereas NEAT does not. This is why it’s expected that on MFP you would log and eat back your exercise calories. As for the differences in other calculators, that’s because they use different calculators to determine your TDEE. Remember that everything is just an estimate.

Yes, but they are all set to sedentary so they would all be then calculating without exercise. I double checked everything was at the lowest. I know they are estimates, and I would believe a variation of 50cal between them, but it gets so drastically different I found that very strange.

Most TDEE calculators take TDEE - a % from that, not a fixed 500 cals. If you set them up as sedentary they still include planned exercise, MFP does not. Now if you enter no exercise at all in the TDEE calcs and chose to maintain weight, then all would be within +/-200 cals. They can differ a bit in the BMR equation used, which a % is applied to that to get to sedentary. They may also use a different multiplier. One may use one BMR euqtion x1.2, whereas another site may use a different BMR calc x1.25.

all these are estimates. pick on, stick with it, if your results after 4-6 weeks are not what would be expected, adjust cals up or down from there.

DX2JX2

they all use slightly different formulas to calculate calorie needs but they should all get you to the same ballpark. Whichever calculator you use, it's important to only use that as a starting point, then to track your results and adjust as needed until you find what works for you.

MFP isn't automatically the answer. It's actually a little low for me...I lose faster than projected when eating at MFP suggested levels. What works for somebody else won't necessary be perfect for you.

kiela64

DX2JX2 wrote: »

they all use slightly different formulas to calculate calorie needs but they should all get you to the same ballpark. Whichever calculator you use, it's important to only use that as a starting point, then to track your results and adjust as needed until you find what works for you.

MFP isn't automatically the answer. It's actually a little low for me...I lose faster than projected when eating at MFP suggested levels. What works for somebody else won't necessary be perfect for you.

Thanks! I knew they were estimates, but I was so surprised to see how wide the variation was. I know if I ate 1800+ it would barely move....but I do think MFP works for me (it has in the past). But it also may be lower by design, I'm not an uber accurate logger, because I don't have a food scale. Idk this is interesting, just something that really caught me by surprise!

cwolfman13

I think you did something wonky in PN...I put my numbers in there and my numbers come very close to what any other calculator gives me...maintenance of 2971 (per my own data it's anywhere between 2800-3000) and 2,441 to get down to 180 by June 1...basically 6 Lbs in 6 weeks. These numbers fairly accurately represent what my own data tells me.

When I put in as more or less sedentary I get just over 2400 maintenance and and just over 1900 to lose 6 Lbs by June 1.

I think you did something wonky with that calculator.

toxikon

They all use different formulas.

I've found this TDEE calculator to be accurate for me: https://www.sailrabbit.com/bmr/

Aaron_K123

kae612 wrote: »

I was keeping MFP at maintenance for a bit as I eased myself back in to tracking, but I wanted to check what lb/week rates I was hitting when I was eating less more consistently. I checked the first few calories-per-day-to-lose-weight calculators that I found on google. PrecisionNutiotion, Calculator.net, TDEE, and a few others. And they all gave me different answers despite using the same stats - 5’2, 200lbs, female, sedentary, etc.

I ended up just changing my goals on mfp a bunch of times to check what they all were, and mfp gave completely different numbers too! I was really surprised by this variance, when aren’t they all going for a 3500 cal = 1 lb of fat, super simple calculation? Especially if I set myself as sedentary for all of them there shouldn’t be any weirdness. But it was all different by about 100cal at least.

I’m absolutely going with MFP. But maybe someone knows why these are all different and what that means?

Edit: I had added examples but it didn’t post for some reason. Anyway, for 2lb/week, PN gives me over 1800cal, for MFP it’s a secret because it’s below 1200, and calculator. Net gives me 915. For 1lb/ week, PN gives me over 2000 which is higher than MFPs maintenance! Mfp gives me 1530, whereas calculator gives me 1427 and TDEE gives me 1433. It’s just all bizarrely different and I’m confused as to why that is.

All sites use 3500 calories equals one pound of fat. But that is CI. CI is objective, 1 pound of fat contains 3500 calories because if you burn 1 pound of fat in a bomb calorimetor it will release enough energy to heat up 3500 liters of water by 1 degree celsius. The variation comes from CO...because concepts like "sedentary" or "lightly active" are nebulous and subjective and different sites are going to interpret that differently. Some are just going to calculate a BMR given a particular formula and them multiply that by some factor and others are going to get there differently. I think MFP takes your activity level to be a simple multiplier on your BMR. BMR isn't objective either, it is an estimation based on population averages and different sites might use different statistics to estimate it. The variation isn't from CI, it is from CO.

Secondly make sure you understand how it is displaying the value. Some sites might take your info and display a target number of calories to hit to lose weight at the rate you entered and some might simply display your maintenance level and asssume you know what to subtract from that.

Also calculators are only as accurate as what you put into them and to be frank it is possible that you simply aren't using them correctly. The difference you got between MFP and PN suggests that is likely the case.

Without actual examples it is hard to know.

rowlandsw

I was talking to a guy at the gym with a fitbit and he said even that seems off when it comes to calories. I'm having doubts about my calories burned on MFP using the exercise log too.

heybales

Most of the TDEE sites use the ancient Harris formula from 1919 study - that has been found outdated many times over - some sites use more recent studies - like MFP does.

So sedentary on the old one is BMR x 1.2, they of course use the Harris BMR formula too - again improvements made on it.

Sedentary on MFP is 1.25, and Mifflin BMR formula.

There's one reason for differences.

Some sites attempt to include differences in daily life in them, most only talk about exercise.
Even there - 4 hrs weekly intense cardio, or 4 hrs walking? Both given equal consideration.

So 2 people with exact same stats and doing 4 hrs of workouts weekly would be given same TDEE - even if one a mail carrier walking route, and one a desk jockey playing video games in the evening.

I attempted daily life as MFP does, and differences in workouts, for getting first estimate.
On my profile page - Just TDEE Please Google sheet. Just copy to your own space.

sssuscello

I use the calculator on IIFYM as I’m a little leery of the estimated calorie burn of MFP. I figure I’ll hit the gym for the amount of days / time I enter and give it my all every time. My Apple Watch shows a totally different burn rate then MFP too.

middlehaitch

toxikon wrote: »

They all use different formulas.

I've found this TDEE calculator to be accurate for me: https://www.sailrabbit.com/bmr/

i was going to post the sailrabbit too.
It gives a number of different formulas and if you click on the ? by each you will get a discription of how the formula works. That may help explain the differences for you.

Cheers, h.